Bloomberg News Miners using a mix of mercury and water to find gold particles in discarded rock in Tanzania. The North Mara mine near the border with Kenya disgorges millions of pounds of waste rock each week, piled high around communities where many people live on less than 40 cents a day. It has been a generation since the rise of environmental economics . Yet even after years of groundbreaking research and support from governmental agencies and nonprofits, the work of such economists has tended to be tangential to the aims of most large conservation organizations. But in the last few years Peter Seligmann, the founder and chairman of Conservation International , has made a major strategic change in his $250 million organization. After two decades of emphasizing the preservation of “hot spots,” or areas with a high level of biodiversity that are threatened with developme...